Production and purification of titanium



United PRODUCTION AND PURIFICATION OF TITANIUM Application August 19, 1952, Serial No. 305,291

Claims priority, application Great Britain September 5, 1951 -3Claims. 01. 75-844) No Drawing.

This invention concerns a process for the production of titanium. It is known that impure metallic titanium can be made by the reduction of titania (either pure, or in a naturally occurring impure form such as rutile), for example by carbon using an electric furnace. The impurities in theproduct, however, especially carbon which may be present in substantial amounts, usually as carbide and/or oxygen, cause it to be brittle and hence of little use in practice. Similarly if the raw material used for the reduction by carbon or any other reducing agent contains a titaniferous ore, an impure titanium alloyed with other constituents is formed, also having properties so much inferior to those of substantially pure titanium that its usefulness in metallurgical practice is very restricted.

It is likewise known that metallic titanium may be prepared by reducing the vapour of titanium tetrachloride under suitable conditions of temperature and pressure with gaseous hydrogen (Fischvoigt and Koref, Zeit. tech. Phys., 6 (1925), 296). The preparation of titanium on a technical scale by this means, however, is attended with great difficulties, since it requires the use either of very high temperatures (which may be in excess of 2000" C.) or else if more moderate temperatures are used, extremely low pressures of titanium tetrachloride. At higher pressures of titanium tetrachloride the equilibria set up are rates Patent such that the formation of metallic titanium by reduction is entirely repressed by the hydrogen chloride formed in the intermediate reduction of the tetrachloride to the triand di-chlorides. If very high temperatures are used, serious problems are encountered in the choice of plant materials so as to ensure purity of the product,-while when using very low partial pressures of titanium tetrachloride the large excess of hydrogen required, makes the energy requirements per unit of titanium produced very great owing to the large amounts of heat required to raise the hydrogen to the reaction temperature. practical difficulties of this process are apparent from the fact, for example, that even if so high a reaction temperature as 2000 C. is used, the yield of metallic titanium becomes negligible if, with a hydrogen pressure of 1 atmosphere, the partial pressure of titanium tetrachloride exceeds a few mms. Such requirements make this. procedure for preparing titanium extremely difii'cult and inefficient, and hence scarcely suited to application on' a technical scale.

We have found, however, that if a gaseous titanium tetrahalide (and especially titanium tetrabromide or tetrachloride) is passed over metallic titanium or a titaniumbearing material (which may be a titanium alloy-preferably free from large amounts of iron--or impure metallic titanium made, for example, by such methods as are described above) under such conditions of temperature and pressure that it is entirely or to a large extent converted to the gaseous titanium dihalide (especially the dibromide or dichloride), or to a mixture of gaseous titanium diand tri-halides, and the product in the gaseous state is The reduced by an excess of hydrogen under suitable conditions of temperature and pressure, metallic titanium (sometimes containing small amounts of hydrogen) is formed by reduction in good yield together with a mixture of hydrogen, hydrogen halide and unreduced titanium dihalide, each of which, after suitable separation, for example, by any of the methods described below, may be used again in the extraction process, which is thus a cyclic one. Production of titanium by this method has the great advantage that it may be carried out at temperatures very much lower, and at partial pressures of titanium halide very much higher than would be possible if the cone sponding tetrahalide had been reduced directly with hy drogen, and therefore is a technically practicable procedure for the manufacture of metallic titanium by the use of hydrogen reduction. Owing to the relatively low temperature of reaction the titanium produced may contain, dependent on the conditions of reaction, small amounts of hydrogen which may easily be removed by subsequent heating of the titanium in vacuo.

In a modification of the process according to the present invention, the gaseous titanium dihalide (or mixture of gaseous titanium diand tri-halides) instead of being formed in the reaction between the titanium tetrahalide vapour and the titanium-bearing material, may be formed by reaction under suitable conditions of temperature and pressure between the titanium-bearing material and a substance which, in the reaction, gives rise to a gaseous titanium dihalide, or a mixture of gaseous lower titanium halides (such substances including for example, bromine, chlorine, hydrogen bromide and hydrogen chloride), and subsequently reducing the gaseous titanium dihalide (or mixture of diand tri-halides) so formed with hydrogen under suitableconditions of temperature and pressure.

The process ;of producing titanium according to the invention therefore consists in reducing the vapour of the dihalides of titanium at elevated temperature with an excess of hydrogen whereby substantially pure titanium condenses with the formation of hydrogen halide which may be recovered and used for the further production of titanium dihalide. We have found it especially advantageous to form the titanium dihalides by means of the reaction between the corresponding unsaturated tetrahalide vapour and titanium bearing material at a low partial pressure, for example in an inert gas stream or in a partial vacuum at elevated temperature.

The expression dihalides of titanium refers to the dichloride, dibromide and di-iodide, and of these the use of the dibromide is preferred because of its high yield at relatively low temperatures, but as shown in the example later the dichloride can also be reduced within technically attainable temperatures and with good yield. Titanium difluoride does not exist. The dihalides are for the reasons outlined above best used without any admixture of the trior tetrahalides, however relatively small amounts of these reduce the yield only to a correspondingly small extent.

The reduction reaction essentially involved in the process according to the present invention is the reduction of a gaseous titanium dihalide by hydrogeni for example,

TiClz (vapour) +H2 (vapour)- Ti (solid, pure) +2HC1 (vapour) In carrying out the process it is especially advantage ous, but not necessary, to select conditions of temperature and pressure which enable more than half of the gaseous titanium dihalide to be reduced to metallic titanium. If the fraction of titanium dihalide reduced is substantially in excess of one half, part of the metallic titanium produced may be used in the process according to the invention so as to produce further titanium dihalide vapour by a reaction with gaseous titanium tetrahalide. To reduce at least one half of the dihalide applied has also the advantage that the condensation of lower titanium halides can easily be avoided, thus eliminating the difliculties encountered when handling these halides.

ln carrying out the process in a cyclic manner, according to the present invention, the gaseous products con taining hydrogen, hydrogen halide, titanium tetrahalide and (if any) lower titanium halides are treated so as to re-apply each constituent in the extraction process. Any lower titanium halides present can be separated from the remaining constituents for example by fractional condensation, and converted to titanium tetrahalide for example by reaction with hydrogen halide or halogen under suitable conditions. These lower halides, when condensed, may also in vacuo or in the stream of an inert gas, such as hydrogen, be decomposed by disproportionation into tetrahalide and metallic titanium; as described above, however, the condensation of these lower halides can be avoided by reducing not less than half of the gaseous titanium dihalide. The processing of the gaseous reaction products so as to recover the hydrogen, hydrogen halide and titanium tetrahalide may be carried out for example by passing the gaseous products under suitable conditions over a titanium-bearing material (for example a titanium alloy, such as ferrotitanium), thereby forming a gaseous mixture containing hydrogen and a titanium tetrahalide, separating the constituents of the mixture (for example by fractional condensation), and re-applying the titanium tetrahalide and the hydrogen separately to the process according to the invention.

An alternative means of recovering these products consists in separating the constituents of the gaseous reaction products (for example by fractional condensation) reapplying the recovered hydrogen and titanium tetrahalide to the process according to the invention, and either converting the recovered hydrogen halide to a gaseous titanium dihalide by reaction under suitable conditions with a titanium-bearing material (preferably free from iron), or else converting it to a titanium tetrahalide by reaction under suitable conditions with a titanium-bearing material (for example ferrotitanium) or a material containing titanium oxide (free or in combination with other oxides) and carbon, purifying the tetrahalidefrom other halides present or from carbon monoxide or both, (for example, by fractional condensation), and subsequently re-applying the tetrahalide to the extraction process according to the invention.

A third method of treatment consists in separating the constituents of the gaseous reaction products, re-applying the recovered hydrogen and titanium tetrahalide to the process according to the invention and converting the hydrogen halide to halogen (for example by reaction with gaseous oxygen), which can then be converted to a titanium tetrahalide (for example by reaction with -a'titanium-bearing material or a mixture of a titania-bearing material with carbon) or else applied directly to the process according to the modification of the process described above.

The following is then an example of -a typical cycle of reactions involved in the process according to the invention:

TiBr4 (vapour) +Ti(solid)- 2TiBrz(vapour) (I) TiBr2(vapour) +H2(vapour)- Ti(solid, pure) +2HBr(vapour) (II) If the gaseous products are passed over a titanium alloy we have:

4HBr(vapour) +Ti( impure alloy) TiBr4+2H2 The solid titanium :(Ti, solid) used for Reaction I may (III) be either pure titanium, for instance part of the product of the process described here, or impure titanium containing carbon and/or oxygen but preferably only minor amounts of iron or metaals of a halogen afiinity greater than or comparable with that of titanium. The impure titanium or titanium alloy (or other material containing available titanium) used for Reactionlil may contain any impurities provided that the tetrahalide formed in the reaction is subsequently subjected to purification, an operation which owing to the volatility of titanium tetra bromide and tetrachloride canveiy effectively be carried out by fractionated distillation.

A combination of suitable temperatures and pressures when carrying out the processaccording to the invention using titanium tetrachloride and bromide may be seen from the following examples. l

l) A stream of argon was saturated with the vapour of titanium tetrachloride at 20 C., and passed over small pieces (3 to 6 mesh) of impure metallic titanium main tained' at about 1150" C. in a reaction chamber made from a refractory material (graphite) and lined with titanium sheet. The gaseous products (containing titanium dichloride and argon) then passed out of this reaction chamber into a separate reaction zone, formed by a graphite tube also lined with titanium sheet, maintained at 1300 C. where they were mixed with hydrogen gas (at approximately 1 atmosphere pressure) in such a proportion that the final partial pressure of titanium dichloride vapourwas about 4 mms. mercury. In this reaction zone reduction occurred and metallic titanium was deposited in the form of a coherent layer readily detached from the underlying titanium sheet. The gaseous products of'the reaction (consisting of unreduced titanium dichloride, hydrogen chloride, hydrogen and argon) passed out of the reaction zone forsubsequent recovery of the constituents. The quantity of titanium deposited. corresponded to about 50% .of the metallic content of the titanium tetrachloride originaily passed.

In a similar experiment in which titanium tetrachloride at a partial pressure of 4 mms. mercury together with hydrogen at a pressure of about 1 atmosphere, was passed through a similar reaction zone maintained at 1300 C. but not previously passed over heated titanium, no deposit of metallic titanium was obtained;

(2) In an experiment in the same reactor, an argon stream containing titanium tetrabromide vapour at a partial pressure of about 10 mm. was passed over small pieces of impure metallic titanium maintained .at about 1150 ,C. The gaseous products (containing titanium dibronn'de) were mixed, at about 1400" .-C., with an excess of hydrogen. at approximately 1 atmosphere pressure) in such proportions that the final Partial pressure of titanium dibromide vapour was about 5 mrns, mercury. Reduction occurred and metallic titanium was deposited as a coherent layer readily detached from the underlying titanium sheet. The quantity of titanium deposited corresponded to about reduction of the titanium dibromide (equivalent to 1.5 times the titanium content of the originally applied titanium tetrabromide).

A similar experiment, in which the titanium .dibromide and excess hydrogen were mixed at 1300" C. also gave metallic titanium, the yield being somewhat lower than when a reduction temperature of 1400 C. was used.

We claim: A

1. Process for the production of metallic titanium which consistsin reducing-the vapour of a titanium tetratitanium halide by contacting and reacting the said tetrahalide vapour with a titanium bearing material of the group consisting of titanium and titanium alloys in any state .of purity at'an elevated temperature above the condensation temperature under the prevailing pressure of "the said lower titanium'halide, and leading the said lower titanium halide vapour into aseparate heated zone where it is reduced to metallic titanium with hydrogen provided in excess at a temperature in accord with the said hydrogen excess which is above the said condensation temperature of the said lower titanium halide and below the temperature to which the said titanium tetrahalide in the presence of the same excess of hydrogen in relation to the said titanium tetrahalide and under the same conditions of pressure must be heated in order to obtain the same degree of conversion of the said titanium tetrahalide to metallic titanium.

2. Process for the production of metallic titanium which consists in reducing the vapour or" titanium tetrabromide with titanium to the vapour of lower titanium bromide by contacting and reacting the said tetrabromide vapour with a titanium bearing material of the group consisting of titanium and titanium alloys in any state of purity at an elevated temperature above the condensation temperature under the prevailing pressure of the said lower titanium bromide, and leading the said lower titanium bromide vapour into a separate heated zone where it is reduced to metallic titanium with hydrogen provided in excess at a temperature in accord with the said hydrogen excess which is above the said condensation temperature of the said lower titanium bromide and below the temperature to which the said titanium tetrahalide in the presence of the same excess of hydrogen in relation to the said titanium tetrahalide and under the same conditions of pressure must be heated in order to obtain the same degree of conversion of the said titanium tetrahalide to metallic titanium.

3. Process for the production of metallic titanium which consists in reducing the vapour of a titanium tetrahalide of the group consisting of the chloride, bromide and iodide with titanium to the vapour of the lower titanium halide by contacting and reacting the said tetrahalide vapour with a titanium bearing material of the group consisting of titanium and titanium alloys in any state of purity at an elevated temperature above the condensation temperature under the prevailing pressure of the said lower titanium halide, leading the said lower titanium halide vapour into a separate heated zone where it is reduced to metallic titanium with hydrogen provided in excess at a temperature in accord with the said hydrogen excess which is above the said condensation temperature of the said lower titanium halide and below the temperature to which the said titanium tetrahalide in the presence of the same excess of hydrogen in relation to the said titanium tetrahalide and under the same conditions of pressure must be heated in order to obtain the same degree of conversion of the said titanium tetrahalide to metallic titanium, and subsequently removing hydrogen absorbed in the titanium produced by heating it in vacuo.

References Cited in the file of this patent UNITED STATES PATENTS 1,306,568 Weintraub June 10, 1912 1,046,043 Weintraub Dec. 3, 1912 1,173,012 Meyer et al. Feb. 22, 1916 2,205,854 Kroll June 25, 1940 2,551,341 Scheer et al May 1, 1951 2,670,270 Jordan Feb. 23, 1954 OTHER REFERENCES Jordan: Abandoned application Ser. No. 165,863,

filed June 2, 1950, cited in Patent No. 2,670,270.

Deutsche Chemische Gesellschaft Berichte, Jahrg. 44, Band 3, October 9-December 11, 1911, pp. 2906-2915.

A Comprehensive Treatise on Inorganic and Theoretical Chemistry by Mellor, vol. VII, pages 11 and 89, published in 1927 by Longmans, Green & Co., 5th Ave., N. Y.

Information Circular 7381, November 1946, pp. 5, 6. Published by Bureau of Mines, D. C.

Titanium, Report of Symposium, December 16, 1948, sponsored by Office Naval Research, Dept. of Navy, Wash, D. C. Publ. March 1949 by OE. of Naval Research, Dept. of Navy, Wash, D. C. Pp. 20-21. 

1. PROCESS FOR THE PRODUCTION OF METALLIC TITANIUM WHICH CONSISTS IN REDUCING THE VAPOUR OF A TITANIUM TETRAHALIDE OF THE GROUP CONSISTING OF THE CHLORIDE, BROMIDE AND IODIDE WITH TITANIUM TO THE VAPOUR OF THE LOWER TITANIUM HALIDE BY CONTACTING AND REACTING THE SAID TETRAHALIDE VAPOUR WITH A TITANIUM BEARING MATERIAL OF THE GROUP CONSITING OF TITANIUM AND TITANIUM ALLOYS IN ANY STATE OF PURITY AT AN ELEVATED TEMPERATURE ABOVE THE CONDENSATION TEMPERATURE UNDER THE PREVAILING PRESSURE OF THE SAID LOWER TITANIUM HALIDE, AND LEADING THE SAID LOWER TITANIUM HALIDE VAPOUR INTO A SEPARATE HEATED ZONE WHERE IT IS REDUCED TO METALLIC TITANIUM WITH HYDROGEN PROVIDED IN EXCESS AT A TEMPERATURE IN ACCORD WITH THE SAID HYDROGEN EXCESS WHICH IS ABOVE THE SAID CONDENSATION TEMPERATURE OF THE SAID LOWER TITANIUM HALIDE AND BELOW THE TEMPERATURE TO WHICH THE SAID TITANIUM TETRAHALIDE IN THE PRESENCE OF THE SAME EXCESS OF HYDROGEN IN RELATION TO THE SAID TITANIUM TETRAHALIDE AND UNDER THE SAME CONDITIONS OF PRESSURE MUST BE HEATED IN ORDER TO OBTAIN THE SAME DEGREE OF CONVERSION OF THE SAID TITANIUM TETRAHALIDE TO METALLIC TITANIUM. 